• 대한치과보철학회지
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• 제44권2호
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• pp.147-156
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• 2006

Statement of problem: The high melting temperature and chemical reactivity of titanium necessitates casting machines different from those used in conventional casting. Despite the new developments in Ti casting systems , inadequate mold filling and internal porosity are frequently observed casting defects. Therefore, the study on the fabrication technique including sprue design to solve these casting defects is still necessary. Purpose: The purpose of this study was to evaluate the effect of sprue design and cross sectional area of sprue on the internal porosity. Materials and methods: 30 simulated cast three units titanium crowns were prepared. 5 cast crowns for each with different sprue design(sinlge sprue, double sprue and plate sprue) of two cross sectional areas (small and large cross sectional areas) were fabricated. The sections of titanium castings were photographed in a microscope at ${\times}100$ magnification to record internal porosities. Results and Conclusion: Within the limits of this study, the following conclusions were drawn: 1. There was a significantly lower in internal porosity of titanium castings for large cross sectional area of sprue group than the small group (P<.05) 2. There was no significant difference in internal porosity among sprue designs in similar cross sectional area of sprue (P>.05).

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.205-208
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• 2007

We injection molded a thin plate with micro prism patterns on its surface and investigated the fidelity of replication of the micro pattern depending on the process parameter such as mold temperature, injection rate or packing pressure. The size of the $90^{\circ}$ prism pattern is $50{\mu}m$ and the size of the plate is $400mm{\times}400mm$. The thickness is 1mm. The fidelity of the replication turned out quite different according to the process parameters and location of the patterns of the plate. We measured the cavity pressure and temperature in real-time during the molding to analyze the effect of the local melt pressure and temperature on the micro pattern replication.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 추계학술대회 논문집
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• pp.88-93
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• 1997

Ball-end milling process is widely used in the die and mold manufacturing because of suitable for the machining of free-form surface. Pencil cutting can eliminate overload in uncut area caused by large diameter of ball-end mill before finish cutting. As the ball-end mill for pencil cutting is long and thin, it is easily deflected by cutting force. The tool deflection when pencil cutting is one of the main reason of the machining errors on a free-from surface. The purpose of the research is to find out the characteristics of deflected cutter trajectory by eddy-current sensor.

• 소성∙가공
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• 제19권3호
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• pp.145-151
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• 2010

In case of thin-wall two-color injection molding, flashing often occurs when molten polymer flows into small gap at the parting line in mold with high pressure or under the unbalanced clamping force condition. In this study, flashing was examined in the production of thin-wall notebook case with large area when the rapid heat cycle molding (RHCM) technology was applied to the two-color injection molding. The effects of the RHCM technology on the part properties and weld-lines were compared with conventional injection molding. The flashing caused by the clamping device of the two-color injection molding machine was examined and compared by experiments and CAE analyses.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.280-283
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• 2002

In the manufacturing of large scale composite structures, the cost-effective processing and the enhancement of structural performance are critical. One of the most effective ways for this purpose is to use stitched multiaxial warp knitted (MWK) perform in the resin transfer molding process. This study reports the effect of stitching on the mechanical properties of MWK composites, and the feasibility processing of the thick U-beam structure utilizing the stitched preforms. Permeability of the preform, viscosity and cure property of the epoxy resin have been measured. The results of resin flow analysis has been used in determining the gate/vent locations of the RTM mold. Cross-sectional observation of the channel beam prototype demonstrated that the resin impregnation was almost complete, except for some surrounding area of stitched yarns.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.563-563
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• 2012

We report a one-step fabrication of single-crystal organic nanowire arrays on substrates using a new direct printing method (liquid-bridge-mediated nanotransfer moulding, LB-nTM), which can simultaneously enable the synthesis, alignment and patterning of the nanowires using molecular ink solutions. Two- or three-dimensional complex structures of various single-crystal organic nanowires were directly fabricated over a large area with a successive process. The position of the nanowires can be aligned easily on complex structures because the mold is movable on substrates before drying the polar liquid layer, which acts as an adhesive lubricant. This efficient manufacturing method can produce a wide range of optoelectronic devices and integrated circuits with single-crystal organic nanowires.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.637-637
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• 2013

We develop single-crystal poly(3,4-ethylenedioxythiopene nanowires using liquid-bridge-mediated nanotransfer printing via vapor phase polymerization. This direct printing method can simultaneously enable the synthesis, alignment and patterning of the nanowires from molecular ink solutions. Twoor three-dimensional complex structures of various single-crystal organic nanowires were directly fabricated over a large area using many types of molecular inks. This method is capable of generating several optoelectronic devices. LB-nTM is based on the direct transfer of various materials from a mold to a substrate via a liquid bridge between them. To demonstrate its usefulness, we used LB-nTM to fabricate nanowire field-effect transistors and arrays of 6,13-bis (triisopropyl- silylethynyl) pentacene (TIPS-PEN) nanowire field-effect transistors.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.632-632
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• 2013

We generated single-crystal organic nanowire arrays using a direct printing method (liquidbridge- mediated nanotransfer molding) that enables the simultaneous synthesis, alignment and patterning of nanowires from molecular ink solutions. Using this method, single-crystal organic nanowires can easily be synthesized by self-assembly and crystallization of organic molecules within the nanoscale channels of molds, and these nanowires can then be directly transferred to specific positions on substrates to generate nanowire arrays by a direct printing process. The position of the nanowires on complex structures is easy to adjust, because the mold is movable on the substrates before the polar liquid layer, which acts as an adhesive lubricant, is dried. Repeated application of the direct printing process can be used to produce organic nanowire-integrated electronics with twoor three-dimensional complex structures on large-area flexible substrates. This efficient manufacturing method is used to fabricate all-organic nanowire field-effect transistors that are integrated into device arrays and inverters on flexible plastic substrates.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.267-270
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• 2009

In the present investigation, we are newly developing a new forming process which can fabricate micro patterns on large-area polymeric substrates for high speed mass production. The key idea of the new process is to pressurize multiple vacuum-packed substrate-mold stacks above the glass transition temperature ($T_g$) of the polymeric substrates. The new process is thought to be promising micro-pattern fabrication technique in three aspects; firstly, isostatic pressing ensures the uniform micro-pattern replicating condition regardless of the substrate area. Secondly, the control of forming condition such as temperature and pressure can realize well-defined process condition exploited in the conventional hot embossing research field. Thirdly, multiple substrates can be patterned at the same time. A prototype forming machine for the new process was developed with the design consideration realizing the present idea. With a developed machine, micro prismatic array patterns with 50 um in size were successfully made on the $380{\times}300{\times}6\;mm$ PMMA plate.

• 한국분말재료학회지
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• 제20권5호
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• pp.355-358
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• 2013

Micro trench structures are applied in gratings, security films, wave guides, and micro fluidics. These micro trench structures have commonly been fabricated by micro electro mechanical system (MEMS) process. However, if the micro trench structures are machined using a diamond tool on large area plate, the resulting process is the most effective manufacturing method for products with high quality surfaces and outstanding optical characteristics. A nonferrous metal has been used as a workpiece; recently, and hybrid materials, including polymer materials, have been applied to mold for display fields. Thus, the machining characteristics of polymer materials should be analyzed. In this study, machining characteristics were compared between nonferrous metals and polymer materials using single crystal diamond (SCD) tools; the use of such materials is increasing in machining applications. The experiment was conducted using a square type diamond tool and a shaper machine tool with cutting depths of 2, 4, 6 and 10 ${\mu}m$ and a cutting speed of 200 mm/s. The machined surfaces, chip, and cutting force were compared through the experiment.